This note focuses on part of Specific Objective 2.8 of the CSEC Biology Syllabus, which asks students about the “role of digestive enzymes in the mouth, stomach and pancreatic enzymes in the small intestine.”

The Mouth

• Enzyme: Salivary Amylase

Secreted by: The Salivary Glands

Function: Starts the digestion of carbohydrates by breaking down starch, a polysaccharide, (example foods: bread and potatoes) into maltose, a disaccharide.

Optimal Temperature: Human body temperature- 37°C

Optimal pH: Near 7.0

The Stomach

• Enzyme: Pepsin

Function: Breaks down proteins (in foods such as fish and eggs) into smaller polypeptides.

Optimal Temperature: Around 37°C

Optimal pH: acidic- near 2.0

• Enzyme: Renin (involved mainly in infants)

Function: Curdling of milk consumed by babies, allowing it to remain in the stomach longer for thorough digestion by gastric enzymes such as pepsin.

Optimal Temperature: Around 37°C

Optimal pH: acidic- between 3.5 to 4.0

The Pancreas

N.B. Pancreatic enzymes are released into the duodenum via the pancreatic duct.

N.B. These enzymes function in the duodenum, not the pancreas.

• Amylase- converts starch (in foods such as pasta) into maltose.
• Lipase- converts fats/lipids (in foods such as butter and oils) into fatty acids and glycerol.
• Trypsin- digestion of proteins into smaller polypeptides as well as amino acids, in foods such as beans and chicken.

Optimal Temperature: Around 37°C

Optimal pH: Slightly alkaline- 7.5-8.0

Small Intestine

• Maltase- breaks down maltose (in foods such as bread) into glucose.
• Sucrase- converts sucrose into glucose and fructose, in foods such as table sugar and sweets.
• Lactase- breaks down lactose (in milk and dairy products) into glucose and galactose.
• Peptidases- digests polypeptides into amino acids, in meat and eggs.

Optimal Temperature: Around 37°C

Optimal pH: Slightly alkaline- 7.5-8.0

Bonus: The Liver (not directly involved in digestion)

• Enzyme: Catalase

Function: Catalase neutralises hydrogen peroxide to prevent it from damaging cells, following the word equation: Hydrogen Peroxide → Water + Oxygen

Optimal Temperature: Around 37°C

Optimal pH: Neutral, near 7.